[PATCH v2] net: cdc_eem: fix tx fixup skb leak

when usbnet transmit a skb, eem fixup it in eem_tx_fixup(),
if skb_copy_expand() failed, it return NULL,
usbnet_start_xmit() will have no chance to free original skb.

fix it by free orginal skb in eem_tx_fixup() first,
then check skb clone status, if failed, return NULL to usbnet.

Fixes: 9f722c0978b0 ("usbnet: CDC EEM support (v5)")
Signed-off-by: Linyu Yuan <redacted>
---

v2: add Fixes tag

 drivers/net/usb/cdc_eem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/usb/cdc_eem.c b/drivers/net/usb/cdc_eem.c
index 2e60bc1b9a6b..359ea0d10e59 100644
--- a/drivers/net/usb/cdc_eem.c
+++ b/drivers/net/usb/cdc_eem.c

@@ -123,10 +123,10 @@ static struct sk_buff *eem_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
 	}
 
 	skb2 = skb_copy_expand(skb, EEM_HEAD, ETH_FCS_LEN + padlen, flags);
+	dev_kfree_skb_any(skb);
 	if (!skb2)
 		return NULL;
 
-	dev_kfree_skb_any(skb);
 	skb = skb2;
 
 done:

-- 
2.25.1

On Thu, Jun 17, 2021 at 07:32:32AM +0800, Linyu Yuan wrote:

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Thu, 17 Jun 2021 07:32:32 +0800 you wrote:

when usbnet transmit a skb, eem fixup it in eem_tx_fixup(),
if skb_copy_expand() failed, it return NULL,
usbnet_start_xmit() will have no chance to free original skb.

fix it by free orginal skb in eem_tx_fixup() first,
then check skb clone status, if failed, return NULL to usbnet.

[...]

Here is the summary with links:
  - [v2] net: cdc_eem: fix tx fixup skb leak
    https://git.kernel.org/netdev/net/c/c3b26fdf1b32

You are awesome, thank you!
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